Ecstasy (MDMA) use has increased sharply among youth in both the US and worldwide. Although the medical literature is replete with studies documenting serious physical consequences associated with ecstasy, little is known about the natural history of ecstasy use and its effects on behavior and mental health. The goal of the proposed research is to contribute critically needed epidemiologic information about the risk factors for becoming an ecstasy user, the patterns of ecstasy use, and its longer-term consequences. The study will also have broader implications for the description and prediction of illicit drug use patterns in general among college students. A longitudinal prospective study of a large sample of college students at the University of Maryland, College Park, a major public University with a diverse student body, will be conducted. The three specific aims of the project are to: 1) identify the predictors of onset of ecstasy use; 2) characterize ecstasy use patterns and develop models to better understand changes in ecstasy use; and 3) describe and predict the consequences of ecstasy use, among college students. A two-stage procedure will be used to recruit students into the study. First, a screening instrument will be administered to all incoming freshman via cooperation with the University's Orientation Office. Second, based on information from the screening, we will recruit 18-19 year old students who fall into three groups and will be eligible for longitudinal follow-up: 1) A "high-risk sample" of non-users of ecstasy at baseline who have used marijuana (Specific Aim# 1); 2) "Prevalent" cases, ecstasy users at baseline, who, in conjunction with incident ecstasy users from Specific Aim# 1 will comprise the sample to study ecstasy use patterns (Specific Aim# 2), and, 3) A "low-risk" sample of non-users of both marijuana and ecstasy at baseline, primarily for comparative purposes for Specific Aim # 3. These students will be assessed annually for three years with a face-to-face interview and semi-annually with mail-in questionnaires. Risk factors that are hypothesized to be related to the initiation of ecstasy use and changes in the pattern of use include family factors (e.g. family history and quality of relationships), social influences (e.g., peer influences, attendance at "raves"), personal characteristics (i.e., behavioral dysreguhtion/sensation-seeking), contextual variables and drug use history. The classes of consequences to be studied in the sample over time are: 1) alcohol and other drug dependence; 2) high risk sexual activity; 3) academic performance; and 4) mental health problems (i.e., anxiety and depression). This study will complement research about the neurobiological mechanisms of risks and consequences of ecstasy use, add to the existing body of knowledge on college drug use, and have important implications for the identification of persons at high risk for ecstasy use and those in need of prevention and early intervention services.